A magnitude 6.2 earthquake which hit the west coast of Canada on Monday night was an aftershock of the magnitude 7.7 quake that struck on Saturday, according to the US Geological Survey (USGS).
A geophysicist said the agency had no immediate reports that the latest quake caused any significant damage or was widely felt.
The National Weather Service West Coast and Alaska Tsunami Warning Centre said that the Monday night quake was not expected to generate a tsunami.
USGS geophysicist Susan Hoover said an even larger aftershock - a magnitude 6.3 quake - was recorded on Sunday in the same general area off British Columbia's Queen Charlotte Islands.
Since the 7.7 quake, Ms Hoover said nearly 80 quakes registering magnitude 4.0 or higher have been recorded in the area.